STATISTICAL EVALUATION OF MONSONS SPHERE IN HEALTHY PERMANENT DENTITIONS IN MAN

The three-dimensional curvature of the mandibular dental arch was stud ied in 20 men and 20 women with sound dentitions and free from temporo mandibular joint problems. The x, y, z coordinates of cusp tips of all but the third molars were obtained with a three-dimensional digitizer , and used to derive a spherical model of the curvature of the occlusa l surfaces. From the best interpolating sphere the radii of the left a nd right curves of Spee (quasi-sagittal plane) and of the canine and m olar curves of Wilson (frontal plane) were computed. The occlusal curv ature of the mandibular arch was not significantly influenced by gende r, even if, on average, all the computed variables were larger in men than women. The radii of the overall sphere, right and left curves of Spee, and curve of Wilson in the molar area were about 105 mm in men, and about 100 mm in women. A relatively large intrasample variability in arch curvature was found. The mean sphere radius in men was very cl ose to the classical value of 4 in, confirming Monson's observations, but the relatively large intrasample variability prevented any definit ive determination of a sexual dimorphism in the three- dimensional cha racteristics of occlusal curvature. (C) 1997 Elsevier Science Ltd.